The instant invention relates to systems and methods for controlling actuation of vehicular safety devices and, more particularly, to a system and method which is capable of identifying specific crash scenarios or "events," the severity of which are better analyzed with event-severity measures other than a universal or "default" event-severity measure.
A variety of systems for actuating vehicular safety devices are well known in the art. Such systems are used to sense a crash condition and, in response to such a condition, to actuate an air bag, or lock a seat belt, or actuate a pretensioner for a seat belt retractor. Typically, the safety device is actuated or deployed into its protective position when an impact exceeding a predetermined magnitude is detected by the actuating system as through the comparison of a given change in one or more physical quantities, such as estimated vehicle velocity or a differential measure such as estimated vehicle jerk, with respective threshold values therefor.
In an improved system and method for crash discrimination taught in copending U. S. patent application Ser. No. 07/773,017 entitled "Predictor/Check Crash Discriminator," a modified vehicle velocity measure is used in combination with an estimate of transitory vehicle jerk to predict a future acceleration value for comparison with a threshold value therefor. More specifically, in this "prediction-based" system and method for crash discrimination, a modified velocity term is used as an event-based timer when predicting a value for future acceleration as the product of a jerk estimate multiplied by event-based time. In this manner, present acceleration information is extrapolated into the future so as to predict when a severe crash is in the making over a wide range of crash types.
Nonetheless, upon encountering certain crash types, such as an event causing a sizable vehicle crush, the resulting negative transitory values for the acceleration information forming the basis for one or more differential measures used in crash discrimination, such as the jerk measures discussed above, may in turn reduce the reliability of actual times-to-fire generated with that measure, specifically, by delaying (or ultimately not otherwise indicating any requirement for) actuation of the safety device. Rather, upon encountering an event causing a sizable vehicle crush, what is needed is a crash discriminator which will employ an alternate or supplemental event-severity measure better suited to analyzing a sizable vehicle crush upon identifying the occurrence thereof.
Similarly, upon encountering a "multiple-hit" event generating a crash waveform broadly characterized by a double hump, the negative intermediate values for the acceleration information again forming the basis of a differential measure such as a jerk measure likewise reduces the reliability of actual times-to-fire generated by known systems and methods which rely upon that differential measure to detect an event requiring actuation of the safety device. Again, what is needed is a crash discriminator which will employ an alternate event-severity measure better suited to analyzing a multiple-hit event upon identifying the occurrence thereof.
Accordingly, what is needed is a crash discriminator capable of identifying the occurrence of special events such as the crushing of the vehicle structure relatively early in a crash event, or a multiple hit scenario, whereupon an alternate or supplemental event-severity measure is used to control actuation of the safety device.